Metabolism is correlative not causative for age-related auditory decline in an insect model

Aging is due to a complex decline of multiple biological processes. Some of the causes include oxidative damage, mitochondrial and proteostatic dysfunction, and DNA damage. The result is that as biological systems age their performance deteriorates. This age-related decline is well quantified, and experienced, for human hearing and is presumed to be due to a decrease in the ears metabolism - specifically a decrease in ability to maintain an electrochemical gradient, the endocochlear potential. However, direct measurements of metabolism across a lifespan in an auditory system are lacking. Even if metabolism does decrease with age, the question remains is it a cause of age-related auditory decline or simply correlative? All auditory systems across the animal kingdom share functional principles including ion pumping cells, auditory receptors, spiking auditory nerves and multiple supporting cells. Therefore, we used an insect, the desert locust, Schistocerca gregaria, as a physiologically versatile model to understand how cellular metabolism correlates with age and impacts on age-related auditory decline. We found that although metabolism correlates with age-related auditory decline it is not causative.